Heat retaining cover



May 27, 1958 G. MBLLER HEAT RETAINING COVER Filed Aug. 9, 1955 GRACE J.MILLER HEAT RETAINING COVER Grace Miller, Tallahassee, Fla.

Application August 9, 1955, Serial No. 527,220

1 Claim. (Cl. S12-284) This invention relates to covers for retainingheat, particularly those for placing over food on a plate which is to betransported an appreciable distance from the kitchen. It will haveparticular usefulness in hospital service where the equipment receivesrough treatment in the hands of poorly paid employees.

A11 important object of the invention is to provide a double-walledcover of heat-retaining type which has an inside surface free fromcracks or crevices which could collect bacteria and an outside surfaceminimizing passage of heat from the space between the walls.

A still further object of the invention is to provide a heat-retainingair space type cover highly suitable for hospital use in which the twomain parts can readily be separated for separate sterilization andwhich, if the outer plastic cover should be broken, it can readily bereplaced for use with the old inner metal ceiling or dome of the cover.

ln the drawings:

Figure l is a central vertical section.

Figure 2 is an enlarged fragmentary sectional view of the peripheraljoint.

Figure 3 is a modification.

The cover consists of two spaced walls, each of a single piece ofmaterial of substantially uniform thickness, and means for detachablylconnecting the two parts together so as to provide a heat insulatingspace between the two walls or domes, the securing means preferablybeing operable without any tools and the entire cover being so made thatthere will be no crevices in which food particles might be caught, asthe device, although having general use, is designed primarily forservice in hospitals where it is important that the cover be very easyto sterilize and where, as here, the outer cover is relatively breakablewith respect to the inner cover so that a new cover can readily beassembled with the other portions. To this end an inner dome is formedof a metal which could be Monel metal, stainless steel, etc., but ispreferably aluminum of a rather high density. This inner shell can be ofany normal shape commonly used for double-walled covers of this type.Itis my preference that the central top surface 11 be very slightlycurved on an extremely large spherical radins, although actually it canbe perfectly at. Likewise, the side walls 12 would follow a curvedformation if the top were spherical, but for ease of manufacturing andfor obtaining maximum space within the cover the side wall is madesubstantially a cylinder as illustrated. Whatever the shape of the metalof the top and the sides, the upper circular junction as at 14 should bea smooth curve.

The outer wall or dome corresponds generally in shape to the inside dome10 but to increase the space between the two walls of the cover I preferthat the distance apart of the two walls at the vertical axis shall begreater than the space 2 1 near the circular top edge of the cover, thisspace 21 being approximately the same transverse dimension as the space22 along the sloping or vertates Patent 2,835,478 Fatented May 27, 1958tical sides of the cover between the two walls. lt is quite important tomake the walls of the cover of qulte different materials and, hence, theouter dome 20 is preferably of a plastic material having a high heatinsulating value, preferably one that will take a smooth nish on theoutside and thick enough to take quite a bit of abuse without damage.The inside surface 15 of the inner dome is preferably highly polished,mirrored as often expressed, as this will relect heat back to the food30 on plate 31.

As a preferable means for joining the two domes to-V gether, a screw 33is permanently carried by the inner dome 10 and extends loosely throughthe plastic outer dome 20. The handle 34 of the cover is of either metalor plastic and is internally threaded as at 35 to serve as a nut tobring the two domes into rm contact at the junction of their lowerperipheral edges and yet be quickly removable without tools for separatesterilization of the two parts whenever that might be required or forreplacement of a broken outer cover.

This peripheral joint at the bottom of the cover is of great importance.It is my preference that the inner metal dome 10 shall curve as at 16,ending in a cylindrical face 17 even with the outer surface 24 of theouter dome. By having the metal project to the margin of the outercover, we will lose a very slight amount of heat to the atmosphere, butin a device of this kind durability is much more of a concern than thevery slight loss in heat. By having the metal edge 17 below the outerdome, the latter is given a very much greater life as the blows thatnormally destroy an outer cover are received at the bottom circular edgeof the cover and such blows `.vill all be taken by the metal and not bythe more easily damaged plastic shell or dome.

The plastic outer dome 20 is molded in such fashion as to provide anenlargement 25 having at its bottom a at annular shoulder 26 which willbe in light contact with a similar annular shoulder 18 on the metalinner dome when the parts are assembled. From the inner edge of theshoulder to the outside margin of the cover both domes have matchingcurves 27 which iirst make contact as the handle 34 is screwed down, theat co-planar surfaces 18 and 26 forming a stop so that when these atsurfaces 1S and 26 are in firm contact the outer cylindrical walls 17and 24 are in perfect registry. It will be noted that the inner face ofthe cover that could get in contact with the food is a smooth, unbrokensurface having no joint or crack of any kind, the screw 33 being securedto the upper surface of the dome and not extending down as far as themirrored surface 15.

In the modification shown in Figure 3, the outer plastic shell is muchthe same as before but its skirt 40 directly touches the serving dish 31and the metallic portion of the cover is quite restricted in size,consisting of an outer metal disk 41 and an inner metal disk 42, thelatter being the bottom wall of the upper air space of the cover. Eachof the plates 41 and 42 are highly polished or mirrored on their lowersurfaces and they are spaced by a separating ring 45 which makes a snugt with the skirt 40 which is preferably conical. The mirrored surface ofdisk 42 reects heat downwardly toward the food and this surface is notaected by the steam which would collect on the bottom surface of plate41. The screw 33 is secured to both disks. In using this modification,it is proposed to use a strong, tough plastic shell.

What I claim is:

A double-walled heat retaining cover for food served on a plate in whichthe two walls are normally secured together to form a single unit, saidcover having an outer wall of a heat insulating plastic having thegeneral shape of a dome with a roof and a skirt, the outer surface ofsaid cover being a smoothly curved surface of revolution ending inV acircular lower edge, and the inner wall of the cover comprises a metalmember ittngV the outer-f dome in a zoneV of contact bounded by asurface of revolution and having a mirrored 4surface, parallel to theplane of the open lower circular edge of the cover to/reect heat;

back'to the food on; the plate, said metal innerY wall having aperipheral edge which vunderlies` the circular Vlower edge oijtheplasticouter wall, whereby-when the walls are as-` sembled, theplasticouter wall is protected against breakage from a blow onrthe loweroutside edge of the cover by Y the underlying metal edge, and readilyseparable threaded vapor from hot food'witbin Ythe cover being smoothland unbroken, thus vavoiding any possibility of lcrevices that mightcollect` bacteria, so that the cover is particularly suitable forhospitaly service.

References Cited in the le of this patent UN'ITED STATES PA'EN'I'SV24,636 Smith July 5,y 1859 Pecor Feb. 5, Sperry Apr. '26, Owens Aug. 15,Oskarnp Feb. 22, Round June 1Y0, Jackson Apr. 24, Montgomery Apr. 24,Werber et alf.y Oct.`2, Bolen Aug. 15, Maersch July 9, Petersonv Sept.17,

t Montgomery May 25,v Maersch Feb. 10,

FOREIGN PATENTSl Y,

Great Britain Apr.'21, Great Britain Mayl 9,Y

Germany Nov. k5,

